Method of making screen printing articles

ABSTRACT

A screen printing article and method of making the article includes using the fibers of the screen to divide the image to be printed into a plurality of dots, the size of each representing the density of the light passing through the screen. Since the fibers of the screen themselves are used to break up the image, each dot being thus created falls substantially centrally in the openings between the fibers. A photographic film is placed adjacent the screen, exposed to the image to be printed and developed. The screen is then coated with a sensitized emulsion, and exposed to light projected through the developed photographic film. The film and the unexposed emulsion are then removed to leave a plurality of openings in the screen, each centrally positioned between the fibers of the screen, through which ink may pass.

United States Patent Lala [451 Feb. 22, 1972 [54] METHOD OF MAKINGSCREEN PRINTING ARTICLES [72] Inventor: Louis A. Lala, 1612 East Third,Dayton,

Ohio 45403 [22] Filed: May 12, 1969 211 Appl. No.: 823,630

2,500,877 4/1950 Sharples 101/1283 Primary Examiner-David KleinAttorney-Marechal, Biebel, French & Bugg [57] ABSTRACT A screen printingarticle and method of making the article includes using the fibers ofthe screen to divide the image to be printed into a plurality of dots,the size of eachrepresenting the density of the light passing throughthe screen. Since the fibers of the screen themselves are used to breakup the image, each dot being thus created falls substantially centrallyin the openings between the fibers. A photographic film is placedadjacent the screen, exposed to the image to be printed and developed.The screen is then coated with a sensitized emulsion, and exposed tolight projected through the developed photographic film. The film andthe unexposed emulsion are then removed to leave a plurality of openingsin the screen. each centrally positioned between the fibers of thescreen, through which ink may pass.

10 Claims, 23 Drawing Figures PATENTEDFEB22 I972 v 3.643 597 SHEET 1 orz FIG-2 H PRIOR ART DEVELOP M/VE/VTUR LOUIS A. LALA A TTOR/VE Y8 METHODOF MAKING SCREEN PRINTING ARTICLES BACKGROUND OF THE INVENTION In theprior art screen printing process, a sensitized emulsion on the screenis exposed to light from a halftone transparency, usually a positive,and thereafter the emulsion is washed to remove all unexposed portions,thus leaving openings in the screen through which ink may pass.

The halftone transparency is usually formed by dividing a continuoustone original picture into a plurality of dots or lines. This is donephotographically by positioning a screen having the desired dot or linenumber between the original picture and a photographic film. This methodof making halftones is common to many printing processes.

In making screen printing plates, however, a moire pattern is formedwhen such a halftone transparency is used, this moire pattern beingparticularly noticeable when the number of dots or lines of the halftonetransparency and the mesh of the screen are in close approximation, thatis, in any ratio less than 1:]. It is common practice, therefore, to usethe ratio 1:4 or I :5 between the number of dots or lines in thetransparency to the mesh openings. Accordingly, a limitation isinherently placed on the number of dots or lines on the halftonetransparency to about 85-100 dots or lines per inch. With a 100 dot orline transparency, for example, the screen would have a mesh density of400-500 openings per inch.

After the halftone transparency is created, it it then oriented relativeto the screen to minimize the moire pattern, although in most cases thispattern is usually not eliminated.

Some of the dots representing highlights in the picture are of smalldiameter, and some of these dots are actually smaller than the diameterof the fibers forming the screen. These small dots, if positioned over afiber, are therefore ineffective in passing ink, thus creating the moirepattern. Also, since some of the dots or openings in the screen mayinclude one or more of the screen fibers, these openings may clog orfill with ink, and some of the smaller openings may clog or fill upcompletely upon the first application of ink to the screen.

Thus, the present screen printing process includes several basicproblems as outlined above, including, for example, the moire patternbetween the halftone transparency and the screen, the limitation on thesize of the screen due to the number of fibers extending across theopenings in the screen, and the inability of the process to reproducefine detail, especially in large production runs or where inks includinglarge metallic particles are used.

A more complete description of the prior art silk screen process, alongwith its advantages and limitations, may be found in the bookPhotographic Screen Process Printing" by Albert Koslofi, 3rd Edition,published by the Signs of the Times Publishing Company, Cincinnati,Ohio.

SUMMARY OF THE INVENTION This invention relates to an improved screenprinting article and method for making the article wherein each openingin the screen is free of obstructions and moire patterns and which istherefore capable of printing pictures of higher quality than heretoforepossible.

The screen printing article of this invention is a screen wherein eachopening in the screen through which ink may flow is substantiallycentered between the fibers forming the screen. The method for preparingthe screen includes the steps of projecting an image from a continuoustone negative through the screen onto a photographically sensitizedsurface. The fibers of the screen will cause the image to be dividedinto a plurality of dots on the surface, each centrally positionedbetween the fibers of the screen. The size of each dot will depend uponthe intensity of the light passing through the fibers at that location.The photographically sensitized surface is then developed and the screenprepared with a sensitized emulsion. Light is then directed through thedeveloped photographic surface onto the screen emulsion, and theemulsion is then washed to clear those areas which have not been exposedto light. Thus, each dot or opening will be located centrally betweenthe fibers since these same fibers were used to create the dots on thephotographic surface.

In one method of practicing the invention, the photographicallysensitized surface is a photographic film which is first placed adjacentthe screen, exposed to the image from a continuous tone picture,removed, developed, and then replaced and aligned in its originalposition, with each dot on the film thus positioned centrally betweenthe fibers of the-screen.

In another method of practicing the invention, a photographic film issecured to the screen by a suitable adhesive, exposed to theimage-forming continuous tone picture through the screen and developedwhile it remains adhered to the screen. Thereafter, the screen is coatedwith a sensitized emulsion which is then exposed to light through thedeveloped film. The film is then physically removed and the screenwashed to remove the unexposed emulsion.

A third method of practicing the invention includes the steps of firstcoating a screen with a clear emulsion and thereafter coating one sideof the screen with a photographically sensitized emulsion, projectingthe image from a continuous tone picture through the screen onto thephotographic emulsion, developing the photographic emulsion while it isin place on the screen, thereafter coating the clear emulsion with asensitizing solution, and then exposing the now sensitized emulsion tolight through the developed photographic emulsion. The screen is thenwashed to remove both the photographically sensitized emulsion and theunexposed portions of the screen emulsion.

In each of the methods described above, a photographic halftone positivefilm is formed utilizing the fibers of the screen to break up the imagefrom a continuous tone picture into a plurality of dots, the size ofeach dot being a function of the intensity of the light through thefibers.

Since each opening in the screen is formed between fibers, no moirepattern is created, and since no fiber extends through any opening, theopenings can be made smaller than heretofore possible, thus permittingthe resultant printed article to be of higher quality. Also, since nofibers extend through the openings, these openings will not tend to clogas quickly as in other processes, thus permitting longer production runsfrom a single screen and the use of such a screen with inks containingrelatively large metallic particles. The improved screen and method formaking this screen can be used either in making single as well asmulticolor prints.

It is therefore an object of this invention to provide an improvedscreen printing article wherein each opening in the article through theink may pass is free of obstructions and is centrally positioned betweenthe fibers forming the article; to provide a method for forming animproved screen printing article of the type described above wherein acontinuous tone picture is projected through the screen onto aphotographically sensitized surface, where the fibers forming the screenbreak up the image into a plurality of dots, the diameter of each dotbeing a function of the intensity of the light through the fibers atthat location, to thereafter expose a sensitized emulsion on the screento light through the developed photographically sensitized surface, andwhere the screen is thereafter washed to remove all unexposed emulsion,thus forming a plurality of openings in the screen, each centrallypositioned between the fibers of the screen.

Other objects and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded pictorial viewshowing the relationship among the original art work, a screen printingplate, a photographically sensitive film, and a table for supportingthese items;

FIGS. 2A and 2B are views illustrating the prior art method of makingscreen printing plates; FIG. 2A showing the relation among the screenprinting plate, the original art work on an image producingtransparency, and the light source; and FIG. 28 showing the openingsformed in a portion of the screen printing plate through which ink maypass;

FIGS. 3A-3F are views showing the steps of one method of 5 DETAILEDDESCRIPTION OF THE PREFERRED EMBODIMENT In Fig. l, a screen plate isstretched on a frame 12 which includes an alignment bracket 13 havingtwo holes 14 and 15 formed therein. While the term silk screen is oftenused in describing this screen printing plate, it will be understoodthat the screen 10 may be formed from many materials including, but notlimited to, silk, nylon, cotton, monofilament synthetic materials, andmetallic fibers.

A vacuum table has mounted thereon a pair of upwardly extending pins 21and 22 each having an outer diameter which matches the inside diameterof the holes 14 and 15, respectively. Thus, when the frame 12 is placedon the table 20, the pins 21 and 22 extend through the openings 14 and15 to hold the frame precisely in place. The table 20 includes atranslucent window 25, and a light source, not shown, is positionedbeneath the window to direct light upwardly through the window onto thescreen printing plate 10 The window 25 may be made from ground glass,polarized glass, or other similar material.

The items which have been described thus far are conventional in theprior art method of making screen printing plates. Typically in priorart processes, the screen has four to five times the mesh relative tothe number of dots or lines used on the halftone positive transparency.The halftone transparency 27 is first oriented relative to the screen 10to minimize the moire pattern created between these two items, and theposition of the transparency is marked. The transparency is thentemporarily removed and the screen coated with a light sensitiveemulsion, such as a synthetic adhesive resin mixed with ammoniumbichromate, such as that sold under the trade name Screen Star, by BondAdhesive Co. Jersey City, NJ. Also, a solution of polyvinyl alcohol,polyvinyl acetate and dibutyl phthalate, and potassium or ammoniumbichromate may be used to coat the screen.

The transparency 27 is then replaced in its previously marked position.As shown in FIG. 2A, the screen is then exposed to light from a lightsource 30 through the transparency. The screen is washed to remove theunexposed areas of emulsion and then dried.

FIG. 2B shows a portion of the screen wherein one unexposed area is arelatively large circular opening 32 which has extending therethrough aplurality of fibers 33 from which the screen 10 is formed. Since the dotsize of the halftone transparency is larger than the mesh of the screen10, one or more of the screen fibers will usually extend across theopening thus formed in the emulsion. In some cases, the size of the dotmay be smaller than the diameter of one of the fibers 33, and if thisopening were positioned above a fiber, then no ink will be permitted topass through the screen at that location.

Returning to FIG. 1, a photographic film has two alignment holes 36 and37 punched therein which are aligned with and which fit precisely overthe alignment pins 21 and 22. This permits the film to be removed andsubsequently replaced in exactly the same position relative to thescreen l0.

The fibers 33 from which the screen 10 is formed should be opaque tothose wavelengths of which the film 35 is sensitive. Thus, metal orblack fibers are opaque to all wavelength of light. When orthochromaticfilm is employed, red fibers may be used to form the screen 10. Thescreen is formed from a plurality of generally equally spaced fibers inorthogonal relationship.

With the film 35 in place on the alignment pins 21 and 22, the screen 10is placed thereover, and a continuous tone negative picture 40 is placeddirectly on the screen 10. It will be understood, however, that it isnot essential that the art work 40 be placed directly on the screen, butonly that the image from a continuous tone picture be directed throughthe screen 10 onto the photographic film 35. Thus, a smaller negative inan enlarger could be employed with the image being projected through thescreen 10 onto the film 35.

In some cases, a spacer 41 is used to insure proper dot formation.Control over light intensity and exposure duration may also be exercisedfor proper dot fonnation. The spacer 41 may be either acetate or glass,and will have a thickness de pending on the spacing between the fibers33, or in other words, the mesh of the screen 10. For a screen having a220 openings per inch, a spacer 0.016 inch thick has been foundsatisfactory. For screens having wider spaces between fibers, a thickerspacer 41 would be used, and conversely, for screens having a high meshcount, thinner spacers may be used. For very high mesh counts, no spacerwould be needed.

Referring now to FIG. 3, I which illustrates clearly one method ofpracticing the invention, the continuous tone negative 40 is placeddirectly on the screen 10, and light from a light source 42 is directeddownwardly through both the negative 40 and the screen 10 onto thephotographic film 35. Preferably, the light from the source 42 iscollamated. Since the fibers 33 from which the screen 10 is formed tendto break up the light into circular dots due to the optical phenomenonof interference, the film 35 will be, when developed, a halftonepositive, with the size of each dot on the film representing theintensity of the light through the fibers at that location. The processfor forming a halftone positive as described above is thus similar tothe conventional practice of forming halftone transparencies by using ascreen between a continuous tone picture and the photographic film.

After exposure, the film 35 is removed from the alignment pins 21 and 22and developed, as shown generally at 45 in FIG. 3B. While the film isbeing developed, the screen 10 is coated with a light sensitive emulsion46. The developed film (FIG. 3C), now designated by reference numeral35a, is replaced on the alignment pins 21 and 22 (FIG. 3D) andpositioned so that each dot on the transparency is centered between thefibers forming the screen. The light source 30 within the table 20 thendirects light through the halftone positive transparency 35a onto thecoated screen 10.

The screen is washed, as designated by reference numeral 47 (FIG. 3E),to clear or remove all unexposed areas. The screen thus formed is driedand each dot or opening in the screen will be found to be positionedcentrally between the fibers forming the screen since it was these samefibers that were used to form the halftone transparency 35a throughwhich the screen was exposed. Thus, each dot 50 in the screen, as shownin FIG. 3F, is located centrally between the fibers 33 forming thescreen. The size of each dot 50 will be a function of the intensity ofthe image at that location.

The method of forming the improved screen printing article describedabove requires that the photographic film be replaced and realignedprior to exposure of the sensitized emulsion on the screen to light.While the alignment pins 21 and, 22 assist in this realignment step,care must always be taken to insure that the dots on the halftonetransparency are each centrally aligned between the fibers.

Another method for making an improved screen printing article is shownin FIG. 4. In this method, a photographic film 55 is temporarily adheredto the screen 10 by a suitable adhesive with the emulsion side in directcontact with the screen. A

continuous tone negative 40 is placed on the opposite side of the screen10, as illustrated in FIG. 4A. The film 55 is exposed to light fromlight source 42 through both the negative 40 and the screen 10. Thenegative 40 is then removed and the film 55 is photographicallydeveloped (FIG. 48) while remaining attached to the screen 10. The filmis then separated from the screen either by inserting a thin sheet ofacetate between film and screen, or by lifting one edge of the film. Thescreen is coated with a sensitized emulsion 46 (FIG. 4C) which is thenallowed to dry, and the film is then returned to its original position.The sensitized emulsion is then exposed to light from a light source 30through the now developed film 55a.

FIG. 5 is an enlarged view of the screen 10 with the film 55a attachedand after the screen has been coated with light sensitive emulsion.Since the film 55 has not been removed from the screen 10, norealignment was necessary after the film is photographically developedinto a halftone positive transparence 55a.

After the emulsion 46 is exposed, the film 55a is removed, and thescreen washed, as shown in FIG. 4D. After it has dried, the silk screenmay be used for printing.

A third method for forming an improved screen printing article accordingto this invention is shown in FIGS. 6 and 7. Here, the screen 10 iscoated with a clear emulsion 60, and after this emulsion has dried, thisemulsion is lightly coated with a waterproof clear, transparent plasticshield, such as that sold under the trade name Krylon, manufactured byKrylon Products, Norristown, Pennsylvania. This clear or transparentemulsion 60 is not photosensitive.

A photographic emulsion 65 is coated on the underneath side of thescreen over the plastic shield. One such photographic emulsion is soldunder the trade name Print-E-Mulsion CB-lOl, and is manufactured byRockland Associates, 333 East 46th Street, New York, NY. A continuoustone negative 40 is then placed on the screen and the photographicemulsion 65 exposed to light from source 42 through both the negative 40and the screen 10. The clear emulsion 60 is water soluble and ispreferably a polyvinyl alcohol, polyvinyl acetate emulsion. Thephotographic emulsion 65 is also water soluble.

After the photographic emulsion 65 is exposed to light, it is developedas shown in FIG. 6B. This developing step removes all but the exposedportions of the photographic emulsion, such as portion 65a in FIG. 7B.The developer used to develop the photographic emulsion 65 should be aslow acting type, such as Selectol, manufactured by Kodak. The type ofdeveloper used will depend, of course, on the type of photographicemulsion employed. During developing, the clear emulsion 60 is leftunaffected due to the protective action of the thin plastic shield. Itwould be desirable, although it is not essential, to use a screenemulsion which is nonsoluble in the solution used to develop thephotographic emulsion.

Again, the photographic emulsion 65, after exposure to light through thescreen 10, will be a halftone positive transparency, with each dot ofthe transparency being centrally located between the fibers of thescreen 10, and the size of each dot will represent the intensity oflight which passes through the fibers of the screen 10.

As shown in FIG. 6C and 7C, the clear emulsion 60 on the screen 10 isthen coated with a sensitizing compound 67 which, in the preferredembodiment is a solution of potassium or ammonium bichromate. Thisphotosensitive compound 67 is not intended to form a separate layer, butis to impregnate and mix with the emulsion 60 to render itphotosensitive. This newly sensitized emulsion is then exposed to lightfrom lamp 30 through the halftone positive transparency 65a. The screen10 is washed (FIG. 6B), and all unexposed portions of the emulsion 60and the remainder of the photographic emulsion 65 are removed, as shownin FIG. 7E.

In each of the above-described methods of forming the improved screenprinting article of this invention, a halftone positive is formed byexposing a photographically sensitive emulsion to light through thescreen which is thereafter coated with a light sensitive emulsion andwhich is then exposed to light, through the thus formed halftonepositive. The screen is washed to remove all unexposed areas, thuscreating a plurality of openings in the screen, each opening beingpositioned centrally between the fibers of the screen. Each openingbeing positioned centrally between the fibers of the screen. Eachopening has a diameter proportional to the intensity of the lightpassing through the fibers forming the screen.

While the continuous tone picture has been described as being a negativelaid adjacent the screen, it is understood that this imagecould also beprojected through the screen from an enlarger, for example. It is alsocontemplated that reversal type photographic emulsions could be employedso that the art work to be printed could be from a positive continuoustone transparency, rather than from a negative. It is also understoodthat this invention can be used in multi as well as single coloredprints.

A screen printing article wherein each opening in the screen is formedby the fibers is therefore more efficient than prior art screen printingdevices since no fiber extends through the opening. This permits thepassage of large particles, such as metallic particles or crystals usedin coating television picture tubes. Also, the openings do not tend tofill as quickly due to the drying of the ink around the edges of theopening. No moire pattern is created at any dot density therebypermitting the screen to be formed with smaller dot sizes, e.g., up to600-800 dots per inch, depending on the availability of screens havingthis mesh number.

While the screen printing article and the methods for making the articledescribed above constitutes the preferred embodiments of the invention,it is to be understood that the invention is not limited to this precisearticle and methods, and the changes may be made therein withoutdeparting from the scope of the invention.

What is claimed is:

l. A method of making a screen printing plate wherein each opening insaid screen is centered between the fibers forming the screen, includingthe steps of projecting an image through said screen onto aphotographically sensitized layer, the fiber of said screen dividingsaid image into a plurality of dots on said layer; developing saidphotographically sensitized layer;

coating said screen with a photosensitive emulsion; projecting lightthrough said developed photographically sensitized layer onto saidscreen coated with emulsion; removing said photographically sensitizedlayer; and washing said emulsion to provide openings in said screen witheach of said openings being centered between the fibers forming thescreen.

2. The method of claim 1 wherein said photographically sensitized layeris a photographic film, the method including the steps of adhering saidfilm to said screen with an adhesive;

wherein the step of developing said photographically sensitized layerincludes developing said film while it is adhered to said screen.

3. The method of claim l'including the steps of coating said screen witha clear transparent emulsion, and coating one surface of said screenwith a photographic emulsion prior to projecting said image through saidscreen;

wherein said step of developing said photographic sensitized layerincludes developing said photographic emulsion while in place on saidscreen;

thereafter applying to said clear transparent emulsion a sensitizingcompound to photosensitize said emulsion; exposing said sensitizedemulsion through said developed photographic emulsion; and

wherein the step of removing said photographically sensitized layeroccurs simultaneously with the washing of said sensitized emulsion.

4. The method of claim 1 wherein said projected image is a negativeimage and wherein a positive is formed on said photographicallysensitized layer.

S. A method of making a screen printing plate wherein each opening inthe screen is centered between fibers forming the screen, including thesteps of attaching a photographic film to said screen;

projecting the image to be printed through said screen onto aphotographic film, the fibers of said screen dividing said image into aplurality of dots on said film;

developing said photographic film while it remains attached to saidscreen;

coating said screen with a sensitized emulsion;

projecting light through said developed photographic film onto saidemulsion; and

washing said emulsion to providing openings in said screen with each ofsaid openings being centered between the fibers forming the screen.

6. The screen printing method of claim wherein the size of each dot is afunction of the intensity of the image at that locatron.

7. The method of claim 5, further including the step of separating saidphotographic film from said screen by a predetermined distance tocontrol the formulation of the dots on said film when said image isprojected through said screen.

8. The method of claim 5 further including the step of controlling theintensity of said image when projecting onto said photographic film tocontrol the formation of dots on said film.

9. The method of making a screen printing plate wherein each opening insaid screen is centered between the fibers forming the screen, includingthe steps of coating said screen with a clear transparent emulsion;

coating one surface of said screen withv a photographic emulsion;projecting the image to be printed through said screen onto saidphotographic emulsion, the fibers of said screen dividing said imageinto a plurality of dots on said emulsion;

developing said photographic emulsion;

applying a photosensitizing substance to said clear emulsion to renderit photosensitive;

directing light through said developed photographic emulsion onto saidsensitized emulsion; and

washing said sensitized emulsion to provide openings in said screen witheach of said openings centrally positioned between the fibers of thescreen.

10. A method of making a screen printing plate wherein each opening insaid screen is centered between the fibers forming the screen, includingthe steps of projecting an image through said screen, onto aphotographic film placed adjacent said screen, the fibers of said screendividing said image into a plurality of dots on said film;

identifying the original relationship between said film and said screen;

removing said film, developing said film, and replacing said film in itsoriginal relation to said screen with the dots thus formed thereonaligned centrally between the fibers of said screen;

coating said screen with a photosensitive emulsion;

projecting light through said developed film onto said emulsion;

removing said film; and

washing said emulsion coated screen to provide openings in said screenwith each of said openings being centered between the fibers forming thescreen.

2. The method of claim 1 wherein said photographically sensitized layer is a photographic film, the method including the steps of adhering said film to said screen with an adhesive; wherein the step of developing said photographically sensitized layer includes developing said film while it is adhered to said screen.
 3. The method of claim 1 including the steps of coating said screen with a clear transparent emulsion, and coating one surface of said screen with a photographic emulsion prior to projecting said image through said screen; wherein said step of developing said photographic sensitized layer includes developing said photographic emulsion while in place on said screen; thereafter applying to said clear transparent emulsion a sensitizing compound to photosensitize said emulsion; exposing said sensitized emulsion through said developed photographic emulsion; and wherein the step of removing said photographically sensitized layer occurs simultaneously with the washing of said sensitized emulsion.
 4. The method of claim 1 wherein said projected image is a negative image and wherein a positive is formed on said photographically sensitized layer.
 5. A method of making a screen printing plate wherein each opening in the screen is centered between fibers forming the screen, including the steps of attaching a photographic film to said screen; projecting the image to be printed through said screen onto a photographic film, the fibers of said screen dividing said image into a plurality of dots on said film; developing said photographic film while it remains attached to said screen; coating said screen with a sensitized emulsion; projecting light through said developed photographic film onto said emulsion; and washing said emulsion to providing openings in said screen with each of said openings being centered between the fibers forming the screen.
 6. The screen printing method of claim 5 wherein the size of each dot is a function of the intensity of the image at that location.
 7. The method of claim 5, further including the step of separating said photographic film from said screen by a predetermined distance to control the formulation of the dots on said film when said image is projected through said screen.
 8. The method of claim 5 further including the step of controlling the intensity of said image when projecting onto said photographic film to control the formation of dots on said film.
 9. The method of making a screen printing plate wherein each opening in said screen is centered between the fibers forming the screen, including the steps of coating said screen with a clear transparent emulsion; coating one surface of said screen with a photographic emulsion; projecting the image to be printed through said screen onto said photographic emulsion, the fibers of said screen dividing said image into a plurality of dots on said emulsion; developing said photographic emulsion; applying a photosensitizing substance to said clear emulSion to render it photosensitive; directing light through said developed photographic emulsion onto said sensitized emulsion; and washing said sensitized emulsion to provide openings in said screen with each of said openings centrally positioned between the fibers of the screen.
 10. A method of making a screen printing plate wherein each opening in said screen is centered between the fibers forming the screen, including the steps of projecting an image through said screen, onto a photographic film placed adjacent said screen, the fibers of said screen dividing said image into a plurality of dots on said film; identifying the original relationship between said film and said screen; removing said film, developing said film, and replacing said film in its original relation to said screen with the dots thus formed thereon aligned centrally between the fibers of said screen; coating said screen with a photosensitive emulsion; projecting light through said developed film onto said emulsion; removing said film; and washing said emulsion coated screen to provide openings in said screen with each of said openings being centered between the fibers forming the screen. 